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Vishnu Technical: Ignition timing control facts
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07-21-2009, 11:47 PM | #221 |
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07-22-2009, 12:55 AM | #223 | ||
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For example, Let us say that your logged fuel trim was +8%. What does that mean? It means that the O2 sensor told the ECU that there was a lean condition detected in closed loop and the ECU added 8% more fuel to bring the the AFR back to 14.7:1 AFR. The ECU does NOT THINK on its own. It reacts to feedback from the sensors by looking at 2d/3d tables that tell it what too do in thousands of contingencies. There is NO idependent thinking or adapting going on. The DME is simply reacting to waht the sensor data and the maps in the DME tell it to do. Change the sensors and the maps and the DME will give you different results. Quote:
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07-22-2009, 01:18 AM | #224 | ||
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If this is the adaptation that BMW folks are refering to, then they are going to be in for a big surprise when their engine give up the ghost from detonation. |
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07-22-2009, 02:45 AM | #225 | |
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Oh by the way the interceptor is not the HW anymore. (I know you like the sneaky way)
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07-22-2009, 02:46 AM | #226 | |
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07-22-2009, 07:46 AM | #227 | |
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This info should be stickied, hah. Is there really such a thing as knock sensor noise or whatever people are claiming? Given the rate at which combustion cycles occur, I wonder if the knock sensor is spot on. |
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07-22-2009, 08:17 AM | #228 |
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Thanks for that explanation Adrian!
In the midst of all these claims and counterclaims, your's is one of the more informative and understandable posts that actually makes a lot of intuitive sense. These timing control arguments remind me of when Shiv first started introducing throttle plate closure management concepts on these forums. It was adamantly contested by some, that throttle plate management was best left to the DME to control in order to maintain BMW's built in safety systems. Of course, the fact that these safety systems were designed to work with stock boost levels was not taken into consideration in their arguments. It only makes sense that as you increase power and boost, the stock design is no longer working with the same stock parameters. This is especially true at part throttle where the piggybacks cannot anticipate every possible throttle angle and load scenario and they fail to completely fool the DME with their offsets. I think that in the end, the fact that throttle plate closure management was emulated by the competition speaks volumes to those who care to listen. I run both tunes and like them both for different reasons. In any case, yours is one of the few posts that is actually understandable to me and makes a lot of intuitive sense. Last time I felt like this was when Shiv began explaining the why's and hows of excessive throttle closure by the DME and how this led to inconsistent performance......it made so much sense at the time. |
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07-22-2009, 08:43 AM | #229 |
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With any given sensor there's always noise/signals that fall outside of the range you are interested in observing/monitoring. Thats the whole point of filters...
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07-22-2009, 09:12 AM | #230 | |
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07-22-2009, 11:39 AM | #233 |
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This is very interesting information but to me it seems more like some..
I mean preemptive controlled timing or not, the JB3 is not a new tune. There are cars out there that have put 10's of thousands of miles on them and very little issues reported back.. |
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07-22-2009, 12:16 PM | #234 | |
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I am in agreement with him on everything else. |
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07-22-2009, 12:21 PM | #235 | |
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It's a bit said when reason, fact and logic get mistaken for scare tactics. Shiv |
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07-22-2009, 12:47 PM | #236 | ||
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Hi Adrian,
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Mike |
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07-22-2009, 12:49 PM | #237 | |
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Mike |
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07-22-2009, 01:00 PM | #239 | |
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Every ECU map that I have looked at has a high octane and low octane timing and fuel maps. When the car is running w/o knock, the ECU uses data from the high octane maps. When the car starts to continuously knocks, the ECU interpolates to the low timing and fuel maps to preserve the engine. In these maps the AFR is richer and the timing is retarded. Maybe the DME is different, but YOU will have to prove it by showing US the maps. You are the one questioning how the proceed works, not us. So please get images of the maps from the DME and post them so we can all see this adaptation that you speak of. Until then you have proved nothing and shown nothing. |
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07-22-2009, 01:02 PM | #240 |
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All these posts and basically here is what it boils down to.
Using the factory knock control to influence timing is bad practice regardless of how sophisticated the knock control system is. Fact is that its a "REACTIVE" system. In order for it to work, knock must occur. All Engine manufacturers use the factory knock control as a backup to their tune not as a primary tuning system. Using CPS offset a hack that apparently works well enough. You are changing timing by changing the reference point. ie if the engine physically is at TDC, you tell the ecu its actually x deg atdc. This in effect reduces the effective ignition timing by x degrees. Fair enough. As for "learing it out" I don't think there is any "learning it out" since timing control is not open loop / closed loop like a/f. Some people say that the ecu/DME will keep adding timing till it senses knock and then back it off. I don't see that as being true. I think what they are confusing it with is the timing trim induced by knock. In other words, if you install a tune and there is no knock the ecu will not trim back any timing. If there is no trim to begin wit there will be no additional timing added. All this being said, there is another facet to CPS offset. Offsetting CPS impacts ignition timing AND fuel injection timing. Since i did not know the effects of injection timing changes i contacted my engineer friends at ISUZU where i previusly worked. I was informed that injection timing affects on fuel consumption and if the change is large on the egts the engine sees. I was also informed that if the change is 4 - 5 deg the effect is not significant. So even though its a hack it works so long as huge changes are not made In other words factory knock sensor based reactive timing control not good, cps based timing control, better but i would not call it "direct control on timing". In fact a piggy is a piggy is a piggy and will never be as good as a flash assuming the DME is cracked fully Harry |
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07-22-2009, 01:05 PM | #241 | |
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07-22-2009, 01:12 PM | #242 | |||
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In other words, complete data including IAT, etc. Quote:
If not that complex, your assertion, if true, would be negated quickly in normal driving. Moderate loads induce little to no CPS offset so the DME would drift back to where it was before any offsetting occurred. But then the next time you got on it, the CPS is there to help. Quote:
And one last time as I see it has been ignored. Why did BMS state the JB3 had a proprietary timing control system that was a direct method which did not exist. This was only stated after CAS was found to not exist in the JB3. Was it was a lie, marketing, or what? Just put this one to bed so we can focus on the test data. |
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